A 5-arm multi-site randomized controlled trial is proposed to clarify the extent to which acupuncture needling can diminish the effect of chronic low back pain on patient functioning and symptoms. Reviews have noted the poor quality of research in this area and urged that scientifically rigorous studies be conducted. Recent higher quality trials suggest acupuncture is a promising treatment for back pain. This study directly addresses methodological shortcomings that have plagued previous studies. Specific aims are to determine, for chronic low back pain, if: 1) acupuncture is more effective than placebo acupuncture, 2) individualized acupuncture is more effective than standardized acupuncture, 3) acupuncture is more effective when needles are inserted in acupuncture points believed effective for chronic low back pain than when needles are inserted in points considered ineffective for chronic low back pain, 4) acupuncture is more effective than usual medical care alone. A total of 1100 subjects (220 per arm) with low back pain lasting at least 3 months will be recruited from group model HMOs in Seattle, Oakland, and Honolulu. They will be randomized to one of two forms of Traditional Chinese Medical acupuncture needling (individualized or standardized), one of two "control" groups (simulated acupuncture or needling of ineffective points), or to continued usual medical care. Ten treatments will be provided over 7 weeks. The primary outcomes, dysfunction and bothersomeness of low back pain, will be measured at baseline, and after 3, 8, 26 and 52 weeks by telephone interviewers masked to treatment. Analysis of covariance within an intention-to-treat context will be used to analyze the data. Because chronic back pain is a major public health problem and the top reason patients seek acupuncture treatment, a clear, unambiguous assessment is critical for making informed decisions about whether acupuncture should be included as part of conventional care for back pain or covered by insurance. Results of this study will provide the clearest evidence to date about the value of acupuncture needling as a treatment for chronic low back pain.